Endoscope light source device and endoscope system

ABSTRACT

An endoscope light source device is constituted by a first light source unit that emits light in a first wavelength band, a second light source unit that emits light in a second wavelength band, a light path combining means for combining the light paths of the light emitted from the first and second light source units, and a light source control means for controlling light emission of the light source units separately. When the light source units are driven to emit light in a first mode, the respective wavelength bands of light are emitted at a first intensity ratio and combined with each other to obtain normal light, which is supplied to an endoscope. Also, when the light source units are driven to emit light in a second mode, the respective wavelength bands of light are emitted at a second intensity ratio having a relatively lower ratio of the light in the second wavelength band, and are combined with each other to obtain special light that has a high light absorption rate in a specific biological tissue, and the special light is supplied to the endoscope.

This application is a continuation of U.S. application Ser. No.15/999,500, filed Aug. 17, 2018, which is the U.S. National Phaseapplication of International Application No. PCT/JP2017/006124, filed onFeb. 20, 2017, which is a continuation of International Application No.PCT/JP2016/054812, filed Feb. 19, 2016, the entire contents of all ofwhich are incorporated herein.

TECHNICAL FIELD

The present disclosure relates to an endoscope light source device andan endoscope system for irradiating a subject with light.

BACKGROUND ART

An endoscope system that can capture special images by changing thespectral intensity characteristics of irradiation light is known. Aspecific configuration of a light source device used in this type ofendoscope system is disclosed in WO 2012/108420 (called “Patent Document1” hereinafter), for example.

The endoscope system described in Patent Document 1 includes a lightsource device that is provided with two light emitting diodes (LEDs) andan optical filter. One of the two LEDs is a purple LED that emits lightin the purple wavelength band. Also, the other LED is a fluorescent LEDthat has a blue LED and a yellow phosphor, and emits pseudo white lightby mixing the blue LED and the yellow fluorescent light. The opticalfilter is a wavelength selection filter that allows only light in aspecific wavelength region to pass, and can be inserted into and removedfrom the light path of irradiation light emitted from the fluorescentLED.

With the light source device described in Patent Document 1, when theoptical filter has been removed from the light path, a subject isirradiated with light emitted from the fluorescent LED as white light,with no limitation of the wavelength band. However, when the opticalfilter is inserted into the light path, the wavelength band of theirradiation light emitted from the fluorescent LED is limited, and thesubject is irradiated with both this irradiation light and theirradiation light emitted from the purple LED. In this way, by changingthe spectral intensity characteristics of the irradiation light andirradiating the subject with only light in a specific wavelength band,it is possible to obtain a captured image in which a specific tissueinside the subject's body is emphasized.

SUMMARY OF DISCLOSURE

With the light source device described in Patent Document 1, in order toobtain irradiation light that has a high intensity in only a specificwavelength band, the wavelength band of the light emitted from thefluorescent LED is limited by the optical filter, thus cutting out lightin unnecessary wavelength bands. The subject is not irradiated with thislight that has been cut out, thus causing the problem that the light useefficiency of the light source device is low. Also, because the opticalfilter allows substantially only light in a specific wavelength band topass, there is a problem that the intensity of the light that passesthrough the optical filter is low, and a bright captured image cannot beobtained.

The present disclosure was achieved in light of the above-describedcircumstances, and an aspect of the present disclosure is to provide anendoscope light source device and an endoscope system in whichirradiation light having a high intensity in only a specific wavelengthband can be emitted with a high light use efficiency.

An endoscope light source device according to an embodiment of thepresent disclosure includes: a first light source unit that emits lightin a first wavelength band; a second light source unit that emits lightin a second wavelength band having a peak wavelength that is differentfrom a peak wavelength of the first wavelength band; a first light pathcombining means for combining a light path of the light emitted from thefirst light source unit and a light path of the light emitted from thesecond light source unit; and a light source control means forcontrolling light emission of the first light source unit and the secondlight source unit separately in accordance with a plurality of modes. Inthis configuration, when the first light source unit and the secondlight source unit are driven by the light source control means to emitlight in a first mode, the light in the first wavelength band and thelight in the second wavelength band are emitted at a first intensityratio and combined by the first light path combining means to obtainnormal light that has a wide wavelength range in a visible light region,and the normal light is supplied to an endoscope, and when the firstlight source unit and the second light source unit are driven by thelight source control means to emit light in a second mode, the light inthe first wavelength band and the light in the second wavelength bandare emitted at a second intensity ratio having a relatively lower ratioof the light in the second wavelength band than the first intensityratio, and are combined by the first light path combining means toobtain special light that has a high light absorption rate in a specificbiological tissue, and the special light is supplied to the endoscope.

According to this configuration, by separately driving the first lightsource unit and the second light source unit to emit light, theirradiation light for irradiation of a subject can be switched betweennormal light, which has a wide wavelength range in the visible lightregion, and special light, in which the light in the wavelength bandhaving a high light absorption rate in a specific biological tissue inthe subject has a higher intensity than the light in other wavelengthbands. Also, when switching the spectral intensity characteristics ofthe irradiation light, there is no need to use an optical filter such asa wavelength limiting filter, thus making it possible to suppress a lossof light that accompanies the switching of the spectral intensitycharacteristics.

Also, in an embodiment of the present disclosure, the endoscope lightsource device further includes: a third light source unit that emitslight in a third wavelength band having a peak wavelength that isdifferent from the peak wavelength of the first wavelength band and thepeak wavelength of the second wavelength band; and a second light pathcombining means for combining a light path of light combined by thefirst light path combining means and a light path of the light emittedfrom the third light source unit, for example. In this configuration, inthe first mode, the light source control means causes the third lightsource unit to emit light at a predetermined intensity ratio withrespect to the first light source unit and the second light source unit,and in the second mode, the light source control means does not causethe third light source unit to emit light.

Also, in an embodiment of the present disclosure, the endoscope lightsource device further includes: a fourth light source unit that emitslight in a fourth wavelength band having a peak wavelength that isdifferent from the peak wavelength of the first wavelength band, thepeak wavelength of the second wavelength band, and the peak wavelengthof the third wavelength band; and a third light path combining means forcombining a light path of light combined by the second light pathcombining means and a light path of the light emitted from the fourthlight source unit, for example. In this configuration, in the firstmode, the light source control means causes the fourth light source unitto emit light at a predetermined intensity ratio with respect to thefirst light source unit, the second light source unit, and the thirdlight source unit, and in the second mode, the light source controlmeans does not cause the fourth light source unit to emit light.

Also, in an embodiment of the present disclosure, the first light sourceunit has a first solid-state light emitting element, and a firstphosphor that is excited by light emitted from the first solid-statelight emitting element and emits light, for example.

Also, in an embodiment of the present disclosure, the second lightsource unit has a second solid-state light emitting element, and asecond phosphor that is excited by light emitted from the secondsolid-state light emitting element and emits light, for example.

Also, in an embodiment of the present disclosure, the second phosphorincludes two phosphors that are excited by the light emitted from thesecond solid-state light emitting element and emit light having mutuallydifferent peak wavelengths, for example.

Also, in an embodiment of the present disclosure, the first solid-statelight emitting element emits light in a purple wavelength band, and thefirst phosphor is a phosphor that emits fluorescent light in a bluewavelength band, for example. In this case, in the light emitted fromthe first light source unit, an intensity of the fluorescent light inthe blue wavelength band is weaker than an intensity of the light in thepurple wavelength band, for example.

Also, an endoscope system according to an embodiment of the presentdisclosure includes any of the endoscope light source devices describedabove, and an endoscope.

According to an embodiment of the present disclosure, an endoscope lightsource device and an endoscope system are provided in which irradiationlight having a high intensity in only a specific wavelength band can beemitted with a high light use efficiency.

BRIEF DESCRIPTION OF DRAWINGS

FIG. 1 is a block diagram showing a configuration of an electronicendoscope system according to a first embodiment of the presentdisclosure.

FIG. 2 is a block diagram showing a configuration of an endoscope lightsource device according to the first embodiment of the presentdisclosure.

FIG. 3 is a block diagram of the endoscope light source device accordingto the first embodiment of the present disclosure.

FIGS. 4A-4B are diagrams showing spectral intensity distribution ofirradiation light emitted from the endoscope light source deviceaccording to the first embodiment of the present disclosure.

FIG. 5 is a block diagram of an endoscope light source device accordingto a second embodiment of the present disclosure.

FIGS. 6A-6B are diagrams showing spectral intensity distribution ofirradiation light emitted from the endoscope light source deviceaccording to the second embodiment of the present disclosure.

FIG. 7 is a block diagram of an endoscope light source device accordingto a third embodiment of the present disclosure.

FIGS. 8A-8B are diagrams showing spectral intensity distribution ofirradiation light emitted from the endoscope light source deviceaccording to the third embodiment of the present disclosure.

FIG. 9 is a block diagram of an endoscope light source device accordingto a fourth embodiment of the present disclosure.

FIGS. 10A-10B are diagrams showing spectral intensity distribution ofirradiation light emitted from the endoscope light source deviceaccording to the fourth embodiment of the present disclosure.

FIG. 11 is a block diagram of an endoscope light source device accordingto a fifth embodiment of the present disclosure.

FIGS. 12A-12B are diagrams showing spectral intensity distribution ofirradiation light emitted from the endoscope light source deviceaccording to the fifth embodiment of the present disclosure.

FIG. 13 is a block diagram of an endoscope light source device accordingto a sixth embodiment of the present disclosure.

FIGS. 14A-14B are diagrams showing spectral intensity distribution ofirradiation light emitted from the endoscope light source deviceaccording to the sixth embodiment of the present disclosure.

FIG. 15 is a block diagram of an endoscope light source device accordingto a seventh embodiment of the present disclosure.

FIGS. 16A-16B are diagrams showing spectral intensity distribution ofirradiation light emitted from the endoscope light source deviceaccording to the seventh embodiment of the present disclosure.

FIGS. 17A-17C are diagrams showing spectral intensity distribution ofirradiation light emitted from an endoscope light source deviceaccording to a variation of the third embodiment of the presentdisclosure.

DESCRIPTION OF EMBODIMENTS

Hereinafter, embodiments of the present disclosure will be describedwith reference to the drawings. Note that an electronic endoscope systemthat includes an endoscope light source device is taken as an example ofan embodiment of the present disclosure in the following description.

First Embodiment

FIG. 1 is a block diagram showing the configuration of an electronicendoscope system 1 that includes an endoscope light source device 201according to a first embodiment of the present disclosure. As shown inFIG. 1, the electronic endoscope system 1 is a system specialized formedical use, and includes an electronic endoscope 100, a processor 200,and a monitor 300.

The processor 200 includes a system controller 21 and a timingcontroller 22. The system controller 21 executes various programs storedin a memory 23 and performs overall control of the electronic endoscopesystem 1. Also, the system controller 21 is connected to an operationpanel 24. The system controller 21 changes operations of the electronicendoscope system 1 and parameters for various operations in accordancewith instructions from an operator that are input using the operationpanel 24. One example of an instruction input by an operator is aninstruction for switching the observation mode of the electronicendoscope system 1. Examples of observation modes include a normalobservation mode and a special observation mode. The observation modeswill be described in detail later. The timing controller 22 outputs aclock pulse, which is for adjustment of the timing of the operations ofportions, to circuits in the electronic endoscope system 1.

The processor 200 includes a light source device 201. FIG. 2 shows ablock diagram of the light source device 201 according to the firstembodiment of the present disclosure. The light source device 201includes a first light source unit 111, a second light source unit 112,and a third light source unit 113. The emission of light by the first tothird light source units 111 to 113 is controlled by first to thirdlight source drive circuits 141 to 143 respectively.

Although the light source device 201 is provided in the processor 200 inthe present embodiment, in another embodiment the light source device201 may be a device that is separate from the processor 200 (or moreaccurately a portion that constitutes an image processing device).

The first light source unit 111 is a purple light emitting diode (LED)that emits light in the purple wavelength band (e.g., wavelengths of 395to 435 nm). The second light source unit 112 has a blue LED 112 a thatemits light in the blue wavelength band (e.g., wavelengths of 425 to 455nm) and a green phosphor 112 b. The green phosphor 112 b is excited byblue LED light emitted from the blue LED 112 a and emits fluorescentlight in the green wavelength band (e.g., wavelengths of 460 to 600 nm).The third light source unit 113 is a red light emitting diode (LED) thatemits light in the red wavelength band (e.g., wavelengths of 630 to 670nm).

Collimator lenses 121 to 123 are arranged in front of, with respect tothe light emission direction, the light source units 111 to 113respectively. The purple LED light emitted from the first light sourceunit 111 is converted into parallel light by the collimator lens 121 andis then incident on a dichroic mirror 131. Also, the light emitted fromthe second light source unit 112, that is to say blue LED light andgreen fluorescent light, is converted into parallel light by thecollimator lens 122 and is then incident on the dichroic mirror 131. Thedichroic mirror 131 combines the light path of the light emitted fromthe first light source unit 111 and the light path of the light emittedfrom the second light source unit 112. Specifically, the dichroic mirror131 has a cutoff wavelength of approximately 430 nm, and has acharacteristic of allowing the passage of light with a shorterwavelength than the cutoff wavelength and reflecting light with awavelength greater than or equal to the cutoff wavelength. For thisreason, the purple LED light emitted from the first light source unit111 passes through the dichroic mirror 131, and the green fluorescentlight emitted from the second light source unit 112 is reflected by thedichroic mirror 131. Accordingly, the light paths of the purple LEDlight and the green fluorescent light are combined with each other. Thelight on the light paths combined by the dichroic mirror 131 is incidenton a dichroic mirror 132.

Also, the red LED light emitted from the third light source unit 113 isconverted into parallel light by the collimator lens 123 and is thenincident on the dichroic mirror 132. The dichroic mirror 132 combinesthe light path of light from the dichroic mirror 131 and the light pathof light emitted from the third light source unit 113. Specifically, thedichroic mirror 132 has a cutoff wavelength of approximately 620 nm, andhas a characteristic of allowing the passage of light with a shorterwavelength than the cutoff wavelength and reflecting light with awavelength greater than or equal to the cutoff wavelength. For thisreason, the light path of the purple LED light and the green fluorescentlight from the dichroic mirror 131 and the light path of the red LEDlight emitted from the third light source unit 113 are combined by thedichroic mirror 132, and the light on the combined light paths isemitted from the light source device 201 as irradiation light L.

FIG. 3 is a block diagram that conceptually shows only the light sourceunits 111 to 113 and the dichroic mirrors 131 and 132 in the lightsource device 201. The green phosphor 112 b of the second light sourceunit 112 is attached to the light emitting surface of the blue LED 112 aand is constituted as a single body with the blue LED 112 a, andtherefore the green phosphor 112 b and the blue LED 112 a are shown asone block in FIG. 3.

Also, the dichroic mirrors 131 and 132 each combine the light paths oflight that has different wavelengths. For this reason, in FIG. 3, thedichroic mirrors 131 and 132 are each denoted by the addition sign “+”.Also, FIG. 3 does not show the collimator lenses 121 to 123 that arearranged in front of the light source units 111 to 113.

The arrows in FIG. 3 denote the light paths of light. In the exampleshown in FIG. 3, the light path of the purple LED light emitted from thefirst light source unit 111 and the light path of the blue LED light andthe green fluorescent light emitted from the second light source unit112 are combined by the dichroic mirror 131. The combined light path ofthe light obtained by the dichroic mirror 131 and the light path of thered LED light emitted from the third light source unit 113 are combinedby the dichroic mirror 132. The light path of the light combined by thedichroic mirror 132 is emitted from the light source device 201 as theirradiation light L.

The irradiation light L emitted from the light source device 201 iscondensed on the entrance surface of an LCB (Light Carrying Bundle) 11by a condensing lens 25, and enters the LCB 11.

The irradiation light L that entered the LCB 11 propagates inside theLCB 11. The irradiation light L that propagated inside the LCB 11 exitsfrom the exit surface of the LCB 11 arranged at the distal end of theelectronic endoscope 100 and passes through a light distribution lens12, and then the subject is irradiated with the irradiation light L.Returning light from the subject, which was irradiated by theirradiation light L from the light distribution lens 12, passes throughan objective lens 13 and forms an optical image on the light receivingsurface of a solid-state image sensor 14.

The solid-state image sensor 14 is a single-plate color CCD (ChargeCoupled Device) image sensor that has a Bayer pixel arrangement. Thesolid-state image sensor 14 accumulates charge according to the lightquantity of an optical image formed on pixels on the light receivingsurface, generates R (Red), G (Green), and B (Blue) image signals, andoutputs the image signals. Note that the solid-state image sensor 14 isnot limited to being a CCD image sensor, and may be replaced with a CMOS(Complementary Metal Oxide Semiconductor) image sensor or another typeof imaging device. The solid-state image sensor 14 may be an elementthat includes a complementary color filter.

A driver signal processing circuit 15 is provided in the connectionportion of the electronic endoscope 100. An image signal regarding thesubject, which was irradiated by light from the light distribution lens12, is input from the solid-state image sensor 14 to the driver signalprocessing circuit 15 at a frame cycle. The frame cycle is 1/30 sec, forexample. The image signal received from the solid-state image sensor 14is subjected to predetermined processing by the driver signal processingcircuit 15 and output to a pre-stage signal processing circuit 26 of theprocessor 200.

The driver signal processing circuit 15 also accesses a memory 16 andreads out unique information regarding the electronic endoscope 100. Theunique information regarding the electronic endoscope 100 recorded inthe memory 16 includes, for example, the pixel count, sensitivity,operable frame rate, and model number of the solid-state image sensor14. The unique information read out from the memory 16 is output by thedriver signal processing circuit 15 to the system controller 21.

The system controller 21 generates control signals by performing variouscomputation based on the unique information regarding the electronicendoscope 100. The system controller 21 uses the generated controlsignals to control the operations of and the timing of various circuitsin the processor 200 so as to perform processing suited to theelectronic endoscope that is connected to the processor 200.

A timing controller 22 supplies a clock pulse to the driver signalprocessing circuit 15 in accordance with timing control performed by thesystem controller 21. In accordance with the clock pulse supplied fromthe timing controller 22, the driver signal processing circuit 15controls the driving of the solid-state image sensor 14 according to atiming synchronized with the frame rate of the images processed by theprocessor 200.

The pre-stage signal processing circuit 26 performs predetermined signalprocessing such as demosaicing processing, matrix computation, and Y/Cseparation on the image signal received in one frame cycle from thedriver signal processing circuit 15, and outputs the result to an imagememory 27.

The image memory 27 buffers image signals received from the pre-stagesignal processing circuit 26, and outputs the image signals to apost-stage signal processing circuit 28 in accordance with timingcontrol performed by the timing controller 22.

The post-stage signal processing circuit 28 performs processing on theimage signals received from the image memory 27 to generate screen datafor monitor display, and converts the generated monitor display screendata into a predetermined video format signal. The converted videoformat signal is output to the monitor 300. Accordingly, subject imagesare displayed on the display screen of the monitor 300.

The electronic endoscope system 1 of the present embodiment has multipleobservation modes, including a normal observation mode and a specialobservation mode. The observation mode is manually or automaticallyswitched according to the subject that is observed. For example, in thecase of observing a subject irradiated with normal light, theobservation mode is switched to the normal observation mode. Note thatnormal light is white light or pseudo white light, for example. Whitelight has a flat spectral intensity distribution in the visible lightrange. Pseudo white light has a spectral intensity distribution that isnot flat, and includes a mixture of colors of light in multiplewavelength bands. In the case of obtaining a captured image in which aspecific biological tissue is emphasized by irradiating the subject withspecial light, for example, the observation mode is switched to thespecial observation mode.

Note that special light is light in a narrow band having a sharp peak ata specific wavelength, for example, and has a high light absorption ratein a specific biological tissue. Examples of specific light wavelengthsinclude light around 415 nm (e.g., 415±5 nm) having a high lightabsorption rate in outer-layer blood vessels, light around 550 nm (e.g.,550±5 nm) having a high light absorption rate in middle-layer bloodvessels that are deeper than those in the outer layer, and light around650 nm (e.g., 650±5 nm) having a high light absorption rate indeep-layer blood vessels that are deeper than those in the middle layer.Note that the longer the wavelength of the light is, the deeper thelight penetrates into the biological tissue. Accordingly, the narrowband light with wavelengths around 415 nm, 550 nm, and 650 nm reachincreasingly deeper regions. The following mainly describes the casewhere outer-layer blood vessels are the biological tissue that is to beemphasized in the special observation mode.

Blood that contains hemoglobin flows through outer-layer blood vessels.Hemoglobin is known to have a peak light absorption rate around 415 nmand 550 nm wavelengths. For this reason, by irradiating the subject withspecial light that is suited to emphasizing outer-layer blood vessels(specifically, light having a high intensity around a wavelength of 415nm, which is the peak light absorption rate of hemoglobin, compared toother wavelength bands), it is possible to obtain a captured image inwhich outer-layer blood vessels are emphasized. Special light having ahigh intensity around a wavelength of 550 nm has a relatively high lightabsorption rate in outer-layer blood vessels as well. In other words,special light having a high intensity around a wavelength of 550 nm alsocontributes to the emphasized display of outer-layer blood vessels. Forthis reason, by irradiating the subject with not only light having awavelength around 415 nm, but also special light having a high intensityaround a wavelength of 550 nm, which is another peak in the lightabsorption rate of hemoglobin, it is possible to increase the luminancein the captured image while also maintaining emphasis of the outer-layerblood vessels.

More specifically, in the special observation mode, by using narrow bandlight (special light) having peaks at special wavelengths, it ispossible to perform narrow band observation that is suited to clearlygrasping the paths of blood vessels that are difficult to observe in thenormal observation mode (blood vessels in various layers such as theouter layer, middle layer, and deep layer). Performing narrow bandobservation obtains information that is useful to the early discovery ofissues such as cancer.

FIGS. 4A-4B show the spectral intensity distributions of the irradiationlight L emitted from the light source device 201 in respectiveobservation modes. FIG. 4A shows the spectral intensity distribution ofthe irradiation light L (normal light) in the normal observation mode,and FIG. 4B shows the spectral intensity distribution of irradiationlight L (special light) in the special observation mode. In FIGS. 4A-4B,the horizontal axis in the spectral intensity distributions indicatesthe wavelength (nm), and the vertical axis indicates the intensity ofthe irradiation light L. Note that the vertical axis is standardizedsuch that the maximum intensity value is 1.

When the electronic endoscope system 1 is in the normal observationmode, all of the light source units 111 to 113 are driven to emit light.The LEDs have sharp spectral intensity distributions that have intensitypeaks at specific wavelengths. Note that in this application, “peakwavelength” refers to the wavelength having the highest intensity amongthe specific wavelengths. For example, if there are two or moreintensity peaks, the peak wavelength is the one of them that has thehighest intensity. A spectral intensity distribution D111 of lightemitted from the first light source unit 111 has a sharp intensitydistribution with a peak wavelength at approximately 415 nm. Also, aspectral intensity distribution D113 of light emitted from the thirdlight source unit 113 has a sharp intensity distribution with a peakwavelength at approximately 650 nm.

Also, a spectral intensity distribution D112 of light emitted from thesecond light source unit 112 has peaks at wavelengths of approximately450 nm and approximately 550 nm. These two peaks are respectively thepeak in the spectral intensity distribution of light emitted from theblue LED 112 a and the spectral intensity distribution of fluorescentlight emitted by the green phosphor 112 b. The spectral intensitydistribution of fluorescent light is largely dependent on the materialthat is used, and spans a wider wavelength band than the spectralintensity distribution of LED light. The green phosphor 112 b in thefirst embodiment has a spectral intensity distribution with a peakwavelength at approximately 550 nm. Note that as shown in FIG. 4A, thepeak wavelength of the second light source unit 112 is approximately 550nm.

Note that in the spectral intensity distribution D112 shown in FIG. 4A,the percentage of the intensity of green fluorescent light intensity ishigher than that of the blue LED light, but the present disclosure isnot limited to this. The percentages of the blue LED light and the greenfluorescent light emitted from the second light source unit 112 can befreely changed by changing the type of green phosphor 112 b and theamount thereof. Also, although the second light source unit 112 has thegreen phosphor 11 b that emits green fluorescent light, the presentembodiment is not limited to this. For example, instead of a greenphosphor, the second light source unit 112 may have a yellow phosphorthat emits yellow fluorescent light having a peak wavelength around 600nm.

Also, although the spectral intensity distributions D111 to D113 shownin FIG. 4A are standardized with a maximum intensity value of 1, thepresent disclosure is not limited to this. The ratio of the intensity oflight emitted from the light sources units 111 to 113 can be setaccording to the observation subject, the imaging mode, or theoperator's preference.

Also, in FIG. 4A, cutoff wavelengths λ131 and λ132 of the dichroicmirrors 131 and 132 are shown by dashed lines. The dichroic mirror 131has the cutoff wavelength λ131 of approximately 430 nm, allows thepassage of light with wavelengths shorter than the cutoff wavelengthλ131, and reflects light with wavelengths longer than or equal to thecutoff wavelength λ131. For this reason, in the spectral intensitydistribution D111 shown in FIG. 4A, light in the wavelength bandindicated by a solid line passes through the dichroic mirror 131, andlight in the wavelength band indicated by a dashed line is reflected bythe dichroic mirror 131. Also, in the spectral intensity distributionD112 shown in FIG. 4A, light with wavelengths that are longer than orequal to the cutoff wavelength λ131 and indicated by a solid line isreflected by the dichroic mirror 131, and light with wavelengths thatare than the cutoff wavelength λ131 and indicated by a dashed linepasses through the dichroic mirror 131.

Also, the dichroic mirror 132 has the cutoff wavelength λ132 ofapproximately 620 nm, allows the passage of light with wavelengthsshorter than the cutoff wavelength λ132, and reflects light withwavelengths longer than or equal to the cutoff wavelength λ132. For thisreason, in the spectral intensity distributions D111 and D112 shown inFIG. 4A, light with wavelengths that are shorter than the cutoffwavelength λ131 and indicated by the solid lines passes through thedichroic mirror 132. Also, in the spectral intensity distribution D112shown in FIG. 4A, light with wavelengths that are longer than or equalto the cutoff wavelength λ132 and indicated by a dashed line isreflected by the dichroic mirror 132. Also, in the spectral intensitydistribution D113 shown in FIGS. 4A-4B, light with wavelengths that arelonger than or equal to the cutoff wavelength λ132 and indicated by asolid line is reflected by the dichroic mirror 132, and light withwavelengths that are shorter than the cutoff wavelength λ132 andindicated by a dashed line passes through the dichroic mirror 132.

In this way, the light paths of light emitted from the light sourceunits 111 to 113 are combined by the dichroic mirror 131 and thedichroic mirror 132, and therefore the light source device 201 emits theirradiation light L (normal light) that has a wide wavelength rangespanning from the ultraviolet region (part of the near ultravioletregion) to the red region. The spectral intensity distribution of thisirradiation light L (normal light) is the combination of the regionsindicated by solid lines in the spectral intensity distributions D111 toD113 shown in FIG. 4A. Irradiating the subject with the irradiationlight L (normal light) makes it possible to obtain a normal colorcaptured image.

Also, when the electronic endoscope system 1 is in the specialobservation mode, the first light source unit 111 and the second lightsource unit 112 are driven to emit light, and the third light sourceunit 113 is not driven to emit light. Moreover, the second light sourceunit 112 is driven to emit light with a smaller drive current and lowerintensity than in the normal observation mode. Accordingly, theintensity at the wavelength of approximately 415 nm, which is the peakof the light absorption rate of hemoglobin, is relatively higher thanthe intensity in the other wavelength bands (i.e., the light is narrowband light), and it is possible to obtain a captured image in whichouter-layer blood vessels are emphasized. Also, the light emitted fromthe second light source unit 112 includes light with a wavelength ofapproximately 550 nm, which is another peak of the light absorption rateof hemoglobin. For this reason, by driving the second light source unit112 to emit light in addition to the first light source unit 111, it ispossible to raise the luminance in the captured image while alsomaintaining the emphasis of outer-layer blood vessels.

In this way, according to the first embodiment, the light source device201 has multiple light sources units 111 to 113 that emit light inmutually different wavelength bands. Also, the light source units 111 to113 are separately driven to emit light according to the imaging mode.For this reason, by selecting the light source units that are to bedriven to emit light and also changing the drive currents of the lightsource units, it is possible to switch the spectral intensitycharacteristics of the irradiation light L to characteristics that arein accordance with the observation mode.

Also, the light paths of the light emitted from the light source units111 to 113 are combined by the dichroic mirrors 131 and 132. Here, thewavelength bands of the light emitted from the light source units 111 to113 are different from each other, and therefore it is possible tominimize the loss of light when the light paths are combined by thedichroic mirrors 131 and 132.

For example, in the special observation mode, in the case of using anoptical filter that allows the passage of substantially only light in aspecific wavelength band as in conventional technology, it is necessaryfor light in wavelength bands other than the specific one to bewastefully emitted, and the light use efficiency of the light sourcedevice is low. In contrast, in the first embodiment of the presentdisclosure, as shown in FIGS. 4A-4B, due to the combination of the lightpaths by the dichroic mirrors 131 and 132, the amount of light that isnot used as the irradiation light L (the light in the regions indicatedby dashed lines in FIGS. 4A-4B) is smaller than the amount of light thatis used as the irradiation light L (the light in the regions indicatedby solid lines in FIGS. 4A-4B). For this reason, with the light sourcedevice 201 of the present embodiment, it is not necessary to wastefullyemit light in wavelength bands that will not be used in irradiation ofthe subject, and a higher light use efficiency than in conventionaltechnology can be achieved.

Also, in the case of observing a site that has a relatively large space(e.g., the stomach), the distance from the distal end portion of theelectronic endoscope 100 to the subject (e.g., the stomach wall) istypically long, and the subject is irradiated with a lower intensity ofirradiation light. In order to obtain a bright captured image, thesubject needs to be irradiated with high-intensity irradiation light.The light source device 201 of the present embodiment does not use anoptical filter in the special observation mode, and has a high light useefficiency, thus making it possible to increase the intensity of theirradiation light with which the subject is irradiated. For this reason,it is possible to obtain a bright captured image even when observing asite such as the stomach.

Also, although the first light source unit 111 is a purple LED thatemits light having a peak wavelength at approximately 415 nm in thefirst embodiment, the present disclosure is not limited to this. Thelight emitted from the first light source unit 111 need only includelight with a wavelength of 415 nm, which is the peak of the lightabsorption rate of hemoglobin, and the first light source unit 111 maybe an LED that emits light with a peak wavelength at 405 nm, forexample. Also, the characteristics of the LEDs and the phosphor of thelight source device 201 can be appropriately changed according to thesubject of observation.

Note that the following are examples of the phosphor in the presentembodiment. Two main types are oxide-based phosphors are nitride-basedphosphors.

Oxide-Based Phosphors

-   -   Yellow phosphors        -   Yellow phosphor having Y₃Al₅O₁₂ (yttrium aluminum oxide) as            a host crystal    -   Green phosphors        -   Green phosphor having Ca₃Sc₂Si₃O₁₂ (calcium scandium silicon            oxide) as a host crystal and activated with Ce        -   Green phosphor having CaSc₂O₄ (calcium scandium oxide) as a            host crystal and activated with Ce

Nitride-Based Phosphors

-   -   Red phosphors        -   Red phosphor in which silicon oxynitride (Si₂N₂O) is            dissolved into calcium aluminum silicon nitride (CaAlSiN₃)            activated with Eu as a host crystal    -   Other phosphors        -   e.g., a sialon phosphor having a ceramic crystal as a matrix            and having a micro-addition of a metal ion that performs            light emission such as a rear earth element, an α-sialon            phosphor that is a solid solution of an α-type silicon            nitride (Si₃N₄) crystal, and a calcium aluminum silicon            nitride phosphor

Second Embodiment

Next, an endoscope light source device according to a second embodimentof the present disclosure will be described. The light source deviceaccording to the second embodiment is also used in the electronicendoscope system 1, similarly to the light source device 201 accordingto the first embodiment.

FIG. 5 is a block diagram conceptually showing only light source unitsand a dichroic mirror in a light source device 202 according to thesecond embodiment. The light source device 202 includes a first lightsource unit 211, a second light source unit 212, and a dichroic mirror231. The emission of light from the light source units 211 and 212 isseparately controlled by a first light source drive circuit and a secondlight source drive circuit, respectively, which are not shown in thefigure.

The first light source unit 211 is a purple LED that emits light in thepurple wavelength band (e.g., wavelengths of 395 to 435 nm). The secondlight source unit 212 has a blue LED that emits light in the bluewavelength band (e.g., wavelengths of 430 to 490 nm), a green phosphor,and a red phosphor. The green phosphor is excited by blue LED lightemitted from the blue LED and emits fluorescent light in the greenwavelength band (e.g., wavelengths of 460 to 600 nm). The red phosphoris excited by blue LED light emitted from the blue LED and emitsfluorescent light in the red wavelength band (e.g., wavelengths of 550to 750 nm). Note that the green phosphor and the red phosphor may bearranged side-by-side along the emission direction of the blue LEDlight, or may be arranged side-by-side in a direction perpendicular tothe emission direction. Also, the materials of the green phosphor andthe red phosphor may be combined to create a single phosphor.

A collimator lens (not shown) is arranged in front of, with respect tothe emission direction, each of the light source units 211 and 212. Thepurple LED light emitted from the first light source unit 211 isconverted into parallel light by the corresponding collimator lens, andis incident on the dichroic mirror 231. Also, the light emitted from thesecond light source unit 212, that is to say the blue LED light and thegreen and red fluorescent light, is converted into parallel light by thecorresponding collimator lens, and is incident on the dichroic mirror231. The dichroic mirror 231 combines the light path of the lightemitted from the first light source unit 211 and the light path of thelight emitted from the second light source unit 212. The light path ofthe light combined by the dichroic mirror 231 is emitted from the lightsource device 202 as the irradiation light L.

FIGS. 6A-6B show the spectral intensity distributions of the irradiationlight L emitted from the light source device 202 in respectiveobservation modes, similarly to FIGS. 4A-4B.

When the electronic endoscope system 1 is in the normal observationmode, both the light source unit 211 and the light source unit 212 aredriven to emit light. A spectral intensity distribution D211 of lightemitted from the first light source unit 211 has a sharp intensitydistribution with a peak wavelength at approximately 415 nm. A spectralintensity distribution D212 of light emitted from the second lightsource unit 212 has peaks at wavelengths of approximately 470 nm,approximately 550 nm, and approximately 630 nm. These three wavelengthsare respectively the peak wavelengths of blue LED light, greenfluorescent light, and red fluorescent light.

Also, in FIG. 6A, a cutoff wavelength λ231 of the dichroic mirror 231 isshown by a dashed line. The dichroic mirror 231 has the cutoffwavelength λ231 of approximately 430 nm, allows the passage of lightwith wavelengths shorter than the cutoff wavelength λ231, and reflectslight with wavelengths longer than or equal to the cutoff wavelengthλ231. For this reason, in the spectral intensity distribution D211 shownin FIG. 4A, light in the wavelength band indicated by a solid linepasses through the dichroic mirror 231, and light in the wavelength bandindicated by a dashed line is reflected by the dichroic mirror 231.Also, in the spectral intensity distribution D212 shown in FIG. 4A,light in the wavelength band indicated by a solid line passes throughthe dichroic mirror 231, and light in the wavelength band indicated by adashed line is reflected by the dichroic mirror 231.

In this way, the light paths of light emitted from the light sourceunits 211 and 212 are combined by the dichroic mirror 231, and thereforethe light source device 202 emits the irradiation light L (normal light)that has a wide wavelength range spanning from the ultraviolet region(part of the near ultraviolet region) to the red region. The spectralintensity distribution of this irradiation light L (normal light) is thecombination of the regions indicated by solid lines in the spectralintensity distributions D211 and D212 shown in FIG. 6A. Irradiating thesubject with this irradiation light L (normal light) makes it possibleto obtain a normal color captured image.

Also, when the electronic endoscope system 1 is in the specialobservation mode, both the first light source unit 211 and the secondlight source unit 212 are driven to emit light. Moreover, the secondlight source unit 212 is driven to emit light with a smaller drivecurrent and lower intensity than in the normal observation mode.Accordingly, in the irradiation light L (special light), the intensityat the wavelength of approximately 415 nm, which is the peak of thelight absorption rate of hemoglobin, is relatively higher than theintensity in the other wavelength bands (i.e., the light is narrow bandlight), and it is possible to obtain a captured image in whichouter-layer blood vessels are emphasized. Also, the light emitted fromthe second light source unit 212 includes light with a wavelength ofapproximately 550 nm, which is another peak of the light absorption rateof hemoglobin. For this reason, by driving the light source unit 212 toemit light in addition to the light source unit 211, it is possible toraise the luminance in the captured image while also maintaining theemphasis of outer-layer blood vessels.

In this way, according to the second embodiment, the light source device202 has multiple light sources units 211 and 212 that emit light inmutually different wavelength bands. Also, the light source units 211and 212 are separately driven to emit light. For this reason, it ispossible to obtain irradiation light L that has a desired spectralintensity distribution by selecting the light source units that are tobe driven to emit light according to the observation mode, and changingthe drive currents of the light source units.

Also, the light source device 202 of the second embodiment has only twolight source units, thus making it possible to simplify theconfiguration of the light source device 202. Moreover, the second lightsource unit 212 has two phosphors, namely green and red phosphors. Forthis reason, when the electronic endoscope system 1 is in the normalobservation mode, the spectral intensity distribution of the irradiationlight L (normal light) more closely approaches a flat distribution inthe visible region than in the case where the second light source unit212 has one phosphor. Accordingly, the subject can be irradiated withirradiation light L (normal light) that is close to natural white light.

Third Embodiment

Next, an endoscope light source device according to a third embodimentof the present disclosure will be described. The light source deviceaccording to the third embodiment is also used in the electronicendoscope system 1, similarly to the light source device 201 accordingto the first embodiment.

FIG. 7 is a block diagram conceptually showing only light source unitsand dichroic mirrors in a light source device 203 according to the thirdembodiment. The light source device 203 includes first to fourth lightsource units 311 to 314 and first to third dichroic mirrors 331 to 333.The emission of light from the light source units 311 to 314 isseparately controlled by first to fourth light source drive circuits,respectively, which are not shown in the figure.

The first light source unit 311 is a purple LED that emits light in thepurple wavelength band (e.g., wavelengths of 395 to 435 nm). The secondlight source unit 312 is a blue LED that emits light in the bluewavelength band (e.g., wavelengths of 430 to 470 nm). The third lightsource unit 313 is a green LED that emits light in the green wavelengthband (e.g., wavelengths of 530 to 570 nm). The fourth light source unit314 is a red LED that emits light in the red wavelength band (e.g.,wavelengths of 630 to 670 nm).

A collimator lens (not shown) is arranged in front of, with respect tothe emission direction, each of the light source units 311 to 314. Thepurple LED light emitted from the first light source unit 311 isconverted into parallel light by the corresponding collimator lens, andis incident on the dichroic mirror 331. Also, the light emitted from thesecond light source unit 312, that is to say the blue LED light, isconverted into parallel light by the corresponding collimator lens, andis incident on the dichroic mirror 331. The dichroic mirror 331 combinesthe light path of the light emitted from the first light source unit 311and the light path of the light emitted from the second light sourceunit 312. The light on the light paths combined by the dichroic mirror331 is incident on the dichroic mirror 332.

Also, the green LED light emitted from the third light source unit 313is converted into parallel light by the corresponding collimator lens,and is incident on the dichroic mirror 332. The dichroic mirror 332combines the light path of light from the dichroic mirror 331 and thelight path of light emitted from the third light source unit 313. Thelight on the light paths combined by the dichroic mirror 332 is incidenton the dichroic mirror 333.

Also, the red LED light emitted from the fourth light source unit 314 isconverted into parallel light by the corresponding collimator lens, andis incident on the dichroic mirror 333. The dichroic mirror 333 combinesthe light path of light from the dichroic mirror 332 and the light pathof light emitted from the fourth light source unit 314. The light pathof the light combined by the dichroic mirror 333 is emitted from thelight source device 203 as the irradiation light L.

FIGS. 8A-8B show the spectral intensity distributions of the irradiationlight L emitted from the light source device 203 in respectiveobservation modes, similarly to FIGS. 4A-4B.

When the electronic endoscope system 1 is in the normal observationmode, the first to fourth light source units 311 to 314 are all drivento emit light. A spectral intensity distribution D311 of the first lightsource unit 311 has a sharp intensity distribution with a peakwavelength at approximately 415 nm. A spectral intensity distributionD312 of the second light source unit 312 has a sharp intensitydistribution with a peak wavelength at approximately 450 nm. A spectralintensity distribution D313 of the third light source unit 313 has asharp intensity distribution with a peak wavelength at approximately 550nm. A spectral intensity distribution D314 of the fourth light sourceunit 314 has a sharp intensity distribution with a peak wavelength atapproximately 650 nm.

Also, in FIG. 8A, cutoff wavelengths λ331 to λ333 of the dichroicmirrors 331 to 333 are shown by dashed lines. The cutoff wavelengthsλ331 to λ333 are respectively 430 nm, 500 nm, and 600 nm. The dichroicmirrors 331 to 333 each allow the passage of light with wavelengthsshorter than the cutoff wavelength, and reflect light with wavelengthslonger than or equal to the cutoff wavelength. The light paths of lightemitted from the light source units 311 to 314 are combined by thedichroic mirrors 331 to 333.

In this way, the light paths of light emitted from the light sourceunits 311 to 314 are combined by the dichroic mirrors 331 to 333, andtherefore the light source device 203 emits the irradiation light L(normal light) that has a wide wavelength range spanning from theultraviolet region (part of the near ultraviolet region) to the redregion. The spectral intensity distribution of this irradiation light L(normal light) is the combination of the regions indicated by solidlines in the spectral intensity distributions D311 to D314 shown in FIG.8A. Irradiating the subject with this irradiation light L (normal light)makes it possible to obtain a normal color captured image.

Also, when the electronic endoscope system 1 is in the specialobservation mode, the first light source unit 311 and the third lightsource unit 313 are driven to emit light, and the second light sourceunit 312 and the fourth light source unit 314 are not driven to emitlight. Moreover, the third light source unit 313 is driven to emit lightwith a smaller drive current and lower intensity than in the normalobservation mode. Accordingly, in the irradiation light L (speciallight), the intensity at the wavelength of approximately 415 nm, whichis the peak of the light absorption rate of hemoglobin, is relativelyhigher than the intensity in the other wavelength bands (i.e., the lightis narrow band light), and it is possible to obtain a captured image inwhich outer-layer blood vessels are emphasized. Also, the light emittedfrom the light source unit 313 includes light with a wavelength ofapproximately 550 nm, which is another peak of the light absorption rateof hemoglobin. For this reason, by driving the light source unit 312 toemit light in addition to the light source unit 311, it is possible toraise the luminance in the captured image while also maintaining theemphasis of outer-layer blood vessels.

In this way, according to the third embodiment, multiple light sourceunits 311 to 314 are provided and emit light in mutually differentwavelength bands. Also, the light source units 311 to 314 are separatelydriven to emit light. For this reason, it is possible to obtainirradiation light L that has a desired spectral intensity distributionby selecting the light source units that are to be driven to emit lightaccording to the observation mode, and changing the drive currents ofthe light source units.

Also, the light source device 203 of the third embodiment has the fourlight source units 311 to 314 that have different wavelength bands andcan be separately controlled to emit light. For this reason, it ispossible to finely control the spectral intensity distribution of theirradiation light L by selecting the light source units that are to bedriven to emit light from among the four light source units 311 to 314,and separately controlling the drive currents when driving the lightsource units to emit light.

Note that in the third embodiment, when the electronic endoscope system1 is in the special observation mode, the second light source unit 312may be driven to emit light with a smaller drive current and lowerintensity than when in the normal observation mode. Because hemoglobinhas a peak in the light absorption rate at approximately 415 nm, it hasa relatively high light absorption also in the nearby blue wavelengthband. For this reason, when in the special observation mode, if thesecond light source unit 312, which emits light in the blue wavelengthband, is driven to emit light, it is possible to increase the luminancein the captured image while also improving the effect of emphasizingouter-layer blood vessels in the captured image.

Fourth Embodiment

In the first to third embodiments, the light source units are dividedinto a light source unit that emits light in the purple wavelength band(a purple LED) and a light source unit that emits light in otherwavelength bands, but the present disclosure is not limited to this. Forexample, the purple LED may include a phosphor. FIG. 9 is a blockdiagram conceptually showing only light source units and dichroicmirrors in a light source device 204 according to the fourth embodimentof the present disclosure. The light source device 204 according to thefourth embodiment is also used in the electronic endoscope system 1 forexample, similarly to the light source device 201 according to the firstembodiment.

As shown in FIG. 9, the light source device 204 includes first to thirdlight source units 411 to 413 and first and second dichroic mirrors 431and 432. The emission of light from the light source units 411 to 413 isseparately controlled by first to third light source drive circuits,respectively, which are not shown in the figure.

The first light source unit 411 has a purple LED that emits light in thepurple wavelength band (e.g., wavelengths of 395 to 435 nm), and a bluephosphor that is excited by purple LED light so as to emit blue (e.g.,wavelengths of 430 to 490 nm) fluorescent light. The second light sourceunit 412 has a blue LED that emits light in the blue wavelength band(e.g., wavelengths of 430 to 470 nm), and a yellow phosphor that isexcited by blue LED light emitted from the blue LED so as to emitfluorescent light in the yellow wavelength band (e.g., wavelengths of500 to 720 nm). The third light source unit 413 has a red LED that emitslight in the red wavelength band (e.g., wavelengths of 620 to 680 nm).

A collimator lens (not shown) is arranged in front of, with respect tothe emission direction, each of the light source units 411 to 413. Thepurple LED light and the blue fluorescent light emitted from the firstlight source unit 411 is converted into parallel light by thecorresponding collimator lens, and is incident on the dichroic mirror431. Also, the blue LED light and the yellow fluorescent light emittedfrom the second light source unit 412 is converted into parallel lightby the corresponding collimator lens, and is incident on the dichroicmirror 431. The dichroic mirror 431 combines the light path of the lightemitted from the first light source unit 411 and the light path of thelight emitted from the second light source unit 412. The light on thelight paths combined by the dichroic mirror 431 is incident on thedichroic mirror 432.

Also, the red LED light emitted from the third light source unit 413 isconverted into parallel light by the corresponding collimator lens, andis incident on the dichroic mirror 432. The dichroic mirror 432 combinesthe light path of light from the dichroic mirror 431 and the light pathof light emitted from the third light source unit 413. The light path ofthe light combined by the dichroic mirror 432 is emitted from the lightsource device 204 as the irradiation light L.

FIGS. 10A-10B show the spectral intensity distributions of theirradiation light L emitted from the light source device 204 inrespective observation modes, similarly to FIGS. 4A-4B.

When the electronic endoscope system 1 is in the normal observationmode, the first to third light source units 411 to 413 are all driven toemit light. A spectral intensity distribution D411 of the first lightsource unit 411 has peak wavelengths at approximately 415 nm and 470 nm.These two wavelengths are respectively the peak wavelengths in thespectral intensity distributions of purple LED light and bluefluorescent light. Here, in the spectral intensity distribution D411,the height of the peak wavelength at approximately 415 nm is set higherthan the height of the peak wavelength at approximately 470 nm. Aspectral intensity distribution D421 of the second light source unit 412has peak wavelengths at approximately 450 nm and 600 nm. These twowavelengths are respectively the peak wavelengths of blue LED light andyellow fluorescent light. A spectral intensity distribution D413 of thethird light source unit 413 has a sharp intensity distribution with apeak wavelength at approximately 650 nm.

Also, in FIG. 10A, cutoff wavelengths λ431 and λ432 of the dichroicmirrors 431 and 432 are shown by dashed lines. The cutoff wavelengthsλ431 and λ432 are respectively 520 nm and 630 nm. The dichroic mirrors431 and 432 each allow the passage of light with wavelengths shorterthan the cutoff wavelength, and reflect light with wavelengths longerthan or equal to the cutoff wavelength. The light paths of light emittedfrom the light source units 411 to 413 are combined by the dichroicmirrors 431 and 432. Note that in the light emitted from the secondlight source unit 412, the blue LED light having a peak wavelength atapproximately 450 nm is shorter than the cutoff wavelength λ431, andtherefore is not included in the light whose light path is combined withanother light path by the dichroic mirror 431.

In this way, the light paths of light emitted from the light sourceunits 411 to 413 are combined by the dichroic mirrors 431 and 432, andtherefore the light source device 204 emits the irradiation light L(normal light) that has a wide wavelength range spanning from theultraviolet region (part of the near ultraviolet region) to the redregion. The spectral intensity distribution of this irradiation light L(normal light) is the combination of the regions indicated by solidlines in the spectral intensity distributions D411 to D413 shown in FIG.10A. Irradiating the subject with this irradiation light L (normallight) makes it possible to obtain a normal color captured image.

Also, when the electronic endoscope system 1 is in the specialobservation mode, the first light source unit 411 and the second lightsource unit 412 are driven to emit light, and the third light sourceunit 413 is not driven to emit light. Moreover, the second light sourceunit 412 is driven to emit light with a smaller drive current and lowerintensity than in the normal observation mode. Accordingly, in theirradiation light L (special light), the intensity at the wavelength ofapproximately 415 nm, which is the peak of the light absorption rate ofhemoglobin, is relatively higher than the intensity in the otherwavelength bands (i.e., the light is narrow band light), and it ispossible to obtain a captured image in which outer-layer blood vesselsare emphasized. Also, the light emitted from the second light sourceunit 412 includes light with a wavelength of approximately 550 nm, whichis another peak of the light absorption rate of hemoglobin. For thisreason, by driving the second light source unit 412 to emit light inaddition to the first light source unit 411, it is possible to raise theluminance in the captured image while also maintaining the emphasis ofouter-layer blood vessels.

Note that the biological tissue in the body cavity that is subjected toimage capturing in the electronic endoscope system 1 normally has anoverall red tint due to blood. For this reason, if the biological tissueis irradiated with red light in the special observation mode, thecaptured image will have a red tint overall, and it will be difficult toobtain an effect of emphasizing outer-layer blood vessels. In thepresent embodiment, the red LED (third light source unit 413) is notdriven to emit light in the special observation mode, thus making itpossible to prevent a reduction in the effect of emphasizing outer-layerblood vessels.

Also, in the present embodiment, in the special observation mode, thesubject is irradiated with light in the blue wavelength band emittedfrom the first light source unit 411. The blue wavelength band does notinclude a wavelength that is a peak in the light absorption rate ofhemoglobin, but is more likely to be absorbed by biological tissue thanred light. For this reason, even if the biological tissue is irradiatedwith blue light in the special observation mode, this has littleinfluence on the effect of emphasizing outer-layer blood vessels. Also,irradiating the subject with blue light makes it possible to raise theluminance in the captured image.

Also, in the present embodiment, in the light emitted from the secondlight source unit 412, the subject is irradiated with only the yellowfluorescent light, and is not irradiated with the blue LED light. On theother hand, the subject is irradiated with light in the blue wavelengthband emitted from the first light source unit 411. For this reason, itis possible to separately change the intensity of light in the bluewavelength band, which has little influence on the effect of emphasizingouter-layer blood vessels, and the intensity of light in the yellowwavelength band, which has a relatively large influence on the sameeffect. Accordingly, in the special observation mode, it is easy toadjust the balance between the effect of emphasizing outer-layer bloodvessels and the brightness of the captured image.

Also, although the second light source unit 412 has a yellow phosphor inthe fourth embodiment, the present disclosure is not limited to this.For example, instead of a yellow phosphor, the second light source unit412 may have a green phosphor that emits green fluorescent light havinga peak wavelength around 550 nm.

Fifth Embodiment

Next, an endoscope light source device according to a fifth embodimentof the present disclosure will be described. The light source deviceaccording to the fifth embodiment is also used in the electronicendoscope system 1, similarly to the light source device 201 accordingto the first embodiment.

FIG. 11 is a block diagram conceptually showing only light source unitsand a dichroic mirror in a light source device 205 according to thefifth embodiment. The light source device 205 includes a first lightsource unit 511, a second light source unit 512, and a dichroic mirror531. The emission of light from the light source units 511 and 512 isseparately controlled by a first light source drive circuit and a secondlight source drive circuit, respectively, which are not shown in thefigure. As shown in FIG. 11, the light source device 205 according tothe fifth embodiment has a configuration in which the red LED (thirdlight source unit 413) and the dichroic mirror 432 are omitted from theconfiguration of the light source device 204 according to the fourthembodiment. Also, the characteristics of the first light source unit511, the second light source unit 512, and the dichroic mirror 531 arethe same as the characteristics of the first light source unit 411, thesecond light source unit 412, and the dichroic mirror 431 of the fourthembodiment.

FIGS. 12A-12B show the spectral intensity distributions of theirradiation light L emitted from the light source device 205 inrespective observation modes, similarly to FIGS. 4A-4B.

As shown in FIGS. 12A-12B, the spectral intensity distributions ofirradiation light L in the fifth embodiment are the same as those of theirradiation light L in the fourth embodiment, with the exception ofomitting red LED light. It should be noted that because the light sourcedevice 205 of the fifth embodiment does not have the dichroic mirror432, the irradiated irradiation light L also includes light in thewavelength band of wavelengths greater than or equal to 630 nm in thelight emitted from the second light source unit 512.

Compared to the light source device 204 of the fourth embodiment, thelight source device 205 of the fifth embodiment can be given a simplerconfiguration to the extent of omitting the red LED (light source unit413) and the dichroic mirror 432. Also, in the light source device 205of the fifth embodiment, light in the red wavelength band of wavelengthslonger than 630 nm in the light emitted from the second light sourceunit 512 is also used as the irradiation light L, thus making itpossible to obtain pseudo white irradiation light L (normal light) inthe normal observation mode even without a red LED.

Also, although the second light source unit 512 has a yellow phosphor inthe fifth embodiment, the present disclosure is not limited to this. Forexample, similarly to the second light source unit 212 in the secondembodiment, the second light source unit 512 may have a green phosphorand a red phosphor instead of a yellow phosphor. In this case, in thenormal observation mode, it is possible to obtain normal light that hasa wider wavelength band than in the case of using a yellow phosphor.

Sixth Embodiment

Next, an endoscope light source device according to a sixth embodimentof the present disclosure will be described. The light source deviceaccording to the sixth embodiment is also used in the electronicendoscope system 1, similarly to the light source device 201 accordingto the first embodiment.

FIG. 13 is a block diagram conceptually showing only light source unitsand dichroic mirrors in a light source device 206 according to the sixthembodiment. The light source device 206 includes first to third lightsource units 611 to 613 and first and second dichroic mirrors 631 and632. The emission of light from the light source units 611 to 613 isseparately controlled by first to third light source drive circuits,respectively, which are not shown in the figure. As shown in FIG. 13,the light source device 206 according to the sixth embodiment has aconfiguration in which the blue LED (second light source unit 312) andthe dichroic mirror 331 are omitted from the configuration of the lightsource device 203 according to the third embodiment, and instead thefirst light source unit 611 is provided with a blue phosphor. Also, thecharacteristics of the first light source unit 611 are the same as thecharacteristics of the first light source unit 511 in the fifthembodiment. Moreover, the characteristics of the second light sourceunit 612, third light source unit 613, the dichroic mirror 631, and thedichroic mirror 632 are respectively the same as the characteristics ofthe third light source unit 313, the fourth light source unit 314, thedichroic mirror 332, and the dichroic mirror 333 of the thirdembodiment.

FIGS. 14A-14B show the spectral intensity distributions of theirradiation light L emitted from the light source device 206 inrespective observation modes, similarly to FIGS. 4A-4B.

As shown in FIGS. 14A-14B, the spectral intensity distributions ofirradiation light L in the sixth embodiment are the same as those of theirradiation light L in the third embodiment, with the exception ofomitting purple LED light and blue LED light, and instead adding purpleLED light and blue fluorescent light emitted from the first light sourceunit 611 (D611). It should be noted that because the light source device206 of the sixth embodiment does not have the dichroic mirror 331, theirradiated irradiation light L also includes light in the wavelengthband of wavelengths greater than or equal to the cutoff wavelength λ331(wavelength of 430 nm) and shorter than a cutoff wavelength λ631(wavelength of 500 nm) in the light emitted from the first light sourceunit 611.

Compared to the light source device 203 of the third embodiment, thelight source device 206 of the sixth embodiment can be given a simplerconfiguration to the extent of omitting the blue LED (light source unit212) and the dichroic mirror 331.

Seventh Embodiment

Next, an endoscope light source device according to a seventh embodimentof the present disclosure will be described. The light source deviceaccording to the seventh embodiment is also used in the electronicendoscope system 1, similarly to the light source device 201 accordingto the first embodiment.

FIG. 15 is a block diagram conceptually showing only light source unitsand dichroic mirrors in a light source device 207 according to theseventh embodiment. The light source device 207 includes first to fourthlight source units 711 to 714 and first to third dichroic mirrors 731 to733. The emission of light from the light source units 711 to 714 isseparately controlled by first to fourth light source drive circuits,respectively, which are not shown in the figure. As shown in FIG. 15,the light source device 207 according to the seventh embodiment has aconfiguration in which the green LED (third light source unit 313) ofthe light source device 203 according to the third embodiment isreplaced with a fluorescent LED that has a blue LED and a yellowphosphor. It should be noted that cutoff wavelengths λ731 to λ733 of thedichroic mirrors 731 to 733 of the seventh embodiment do not need to bethe same as λ331 to λ333 of the dichroic mirrors 331 to 333 of the thirdembodiment. Specifically, the cutoff wavelengths λ731 to λ733 may beappropriately set so as to reduce light loss during the combination oflight paths by the dichroic mirrors 731 to 733, or so as to obtain adesired spectral intensity distribution for the irradiation light L.

FIGS. 16A-16B show the spectral intensity distributions of theirradiation light L emitted from the light source device 207 inrespective observation modes, similarly to FIGS. 4A-4B.

As shown in FIGS. 16A-16B, the spectral intensity distributions ofirradiation light L in the seventh embodiment are the same as those ofthe irradiation light L in the third embodiment, with the exception of aspectral intensity distribution D713 of light emitted from the thirdlight source unit 713. It should be noted that the cutoff wavelengthsλ731 to λ733 of the dichroic mirrors 731 to 733 of the seventhembodiment are different from λ331 to λ333 of the dichroic mirrors 331to 333 of the third embodiment. For this reason, the spectral intensitydistributions of light emitted as the irradiation light L (the regionsshown by solid lines in the spectral intensity distribution shown inFIGS. 16A-16B) are different from the spectral intensity distributionsof the irradiation light L in the third embodiment.

Unlike the light source device 203 of the third embodiment, the lightsource device 207 of the seventh embodiment uses a fluorescent LED(third light source unit 713) instead of a green LED (third light sourceunit 313), and therefore the spectral intensity distribution of theirradiation light L (normal light) closely approaches a flatdistribution in the visible range. Accordingly, the subject can beirradiated with irradiation light L (normal light) that is close tonatural white light.

Also, although the third light source unit 713 has a yellow phosphor,the present disclosure is not limited to this. For example, instead of ayellow phosphor, the third light source unit 713 may have a greenphosphor that has a peak wavelength around 550 nm and a red phosphorthat has a peak wavelength around 650 nm. Alternatively, the third lightsource unit 713 may have a yellow phosphor that is intense in a widerwavelength band than that shown in FIGS. 16A-16B.

Illustrative embodiments of the present disclosure have been describedabove. The embodiments of the present disclosure are not limited to theembodiments described above, and various changes can be made withoutdeparting from the scope of the technical idea of the presentdisclosure. For example, appropriate combinations of embodiments and thelike explicitly given as examples in this specification and obviousembodiments and the like are also encompassed in embodiments of thepresent disclosure. For example, LEDs are envisioned as the solid-statelight emitting elements in the above embodiments. The present disclosureis not limited to this, and LDs (Laser Diodes) can also be employed asthe solid-state light emitting elements.

FIGS. 17A-17C show the spectral intensity distributions of theirradiation light L emitted from the light source device 203 in avariation of the third embodiment. In the present variation, there arethree observation modes (the normal observation mode, a first specialobservation mode, and a second special observation mode). FIG. 17A showsthe spectral intensity distribution of the irradiation light L (normallight) in the normal observation mode, FIG. 17B shows the spectralintensity distribution of the irradiation light L (special light) in thefirst special observation mode, and FIG. 17C shows the spectralintensity distribution of the irradiation light L (special light) in thesecond special observation mode. In FIGS. 17A-17D, the horizontal axisin the spectral intensity distributions indicates the wavelength (nm),and the vertical axis indicates the intensity of the irradiation lightL. Note that the vertical axis is standardized such that the maximumintensity value is 1.

The operations in the normal observation mode are the same as in thethird embodiment, which were described using FIGS. 7 and 8A-8B.Accordingly, in the normal observation mode, irradiation light L (normallight) having the same spectral characteristics as in FIG. 8A isemitted. Irradiating the subject with this irradiation light L (normallight) makes it possible to obtain a normal color captured image.

The operations in the first special observation mode are the same asthose in the special observation mode in the third embodiment, whichwere described using FIGS. 7 and 8A-8B. Accordingly, in the firstspecial observation mode, irradiation light L (special light) having thesame spectral characteristics as in FIG. 8B is emitted. It is thereforepossible to obtain a captured image in which mainly outer-layer bloodvessels are emphasized.

When the electronic endoscope system 1 is in the second specialobservation mode, the fourth light source unit 314 is driven to emitlight, and the first to third light source units 311 to 313 are notdriven to emit light. Accordingly, in the irradiation light L (speciallight), the percentage of light at the wavelength of approximately 650nm, which is the peak of the light absorption rate of hemoglobin, isrelatively higher (i.e., the light is narrow band light having a peak atonly a wavelength of approximately 650 nm), and it is possible to obtaina captured image in which mainly deep-layer blood vessels areemphasized.

The invention claimed is:
 1. An endoscope light source devicecomprising: a first light source unit configured to emit violet lighthaving a first peak wavelength in a violet wavelength band; a secondlight source unit configured to emit green light having a second peakwavelength in a green wavelength band; a light path combiner configuredto combine light emitted along a first light path by the first lightsource unit with at least light emitted along a second light path by thesecond light source unit to produce combined light; and light sourcedrive circuitry configured to control the first light source unit toemit the violet light, and to separately control the second light sourceunit to emit the green light, in accordance with a plurality of modes,wherein the endoscope light source device is configured to supply thecombined light to an endoscope, and wherein, when the first light sourceunit and the second light source unit are driven by the light sourcedrive circuitry to emit light in a first mode of the plurality of modes,the violet light and the green light are emitted at a first intensityratio, and the combined light is normal light that has the first peakwavelength and the second peak wavelength, and wherein, when the firstlight source unit and the second light source unit are driven by thelight source drive circuitry to emit light in a second mode of theplurality of modes, the violet light and the green light are emitted ata second intensity ratio having a relatively lower proportion of thegreen light than the first intensity ratio, and the combined light isspecial light, and wherein the normal light includes a wider range ofvisible light wavelengths than the special light does, and wherein alight absorption rate of the special light in blood vessels is higherthan a light absorption rate of the normal light in the blood vessels.2. The endoscope light source device according to claim 1, wherein thefirst peak wavelength is one of 405 nm and 415 nm.
 3. The endoscopelight source device according to claim 1, wherein the second peakwavelength is 550 nm.
 4. The endoscope light source device according toclaim 1, wherein the light path combiner comprises a dichroic mirrorconfigured to combine the light emitted along the first light path withthe light emitted along the second light path.
 5. The endoscope lightsource device according to claim 4, wherein a cutoff wavelength of thedichroic mirror is a wavelength between the first peak wavelength andthe second peak wavelength.
 6. The endoscope light source deviceaccording to claim 1, wherein an intensity of the second peak wavelengthin the special light is less than half of an intensity of the first peakwavelength in the special light.
 7. The endoscope light source deviceaccording to claim 1, further comprising: a third light source unitconfigured to emit blue light having a third peak wavelength in a bluewavelength band; and a fourth light source unit configured to emit redlight having a fourth peak wavelength in a red wavelength band, whereinthe light path combiner is configured to combine the light emitted alongthe first light path and the light emitted along the second light pathwith light emitted along a third light path by the third light sourceunit and light emitted along a fourth light path by the fourth lightsource unit to produce the combined light, wherein, when the first lightsource unit, the second light source unit, the third light source unitand the fourth light source unit are driven by the light source drivecircuitry to emit light in the first mode, the combined light is normallight that has a wide range of visible light wavelengths and further hasthe first peak wavelength, the second peak wavelength, the third peakwavelength and the fourth peak wavelength.
 8. The endoscope light sourcedevice according to claim 1, wherein the first light source unitcomprises a first light-emitting diode, and the second light source unitcomprises a second light-emitting diode.
 9. An endoscope systemcomprising: the endoscope light source device according to claim 1; andan endoscope.
 10. An endoscope light source device comprising: a firstlight source unit configured to emit first wavelength band light; asecond light source unit configured to emit second wavelength bandlight, wherein a light absorption rate in outer-layer blood vessels ishigher for a first peak wavelength in the first wavelength band lightthan for a second peak wavelength in the second wavelength band light,and wherein a light absorption rate in middle-layer blood vessels ishigher for the second peak wavelength than for the first peakwavelength; a light path combiner configured to combine light emittedalong a first light path by the first light source unit with at leastlight emitted along a second light path by the second light source unitto produce combined light; and light source drive circuitry configuredto control the first light source unit to emit the first wavelength bandlight, and to separately control the second light source unit to emitthe second wavelength band light, in accordance with a plurality ofmodes, wherein the endoscope light source device is configured to supplythe combined light to an endoscope, and wherein, when the first lightsource unit and the second light source unit are driven by the lightsource drive circuitry to emit light in a first mode of the plurality ofmodes, the first wavelength band light and the second wavelength bandlight are emitted at a first intensity ratio, and the combined light isnormal light that has the first peak wavelength and the second peakwavelength, and wherein, when the first light source unit and the secondlight source unit are driven by the light source drive circuitry to emitlight in a second mode of the plurality of modes, the first wavelengthband light and the second wavelength band light are emitted at a secondintensity ratio having a relatively lower proportion of the secondwavelength band light than the first intensity ratio, and the combinedlight is special light, and wherein a penetration depth of light into abiological tissue is lower for the first wavelength band light, and ishigher for the second wavelength band light, than for light of a bluewavelength band, and wherein the normal light includes a wider range ofvisible light wavelengths than the special light does, and wherein alight absorption rate in blood vessels is higher for the special lightthan for the normal light.
 11. The endoscope light source deviceaccording to claim 10, wherein the first peak wavelength is one of 405nm and 415 nm.
 12. The endoscope light source device according to claim10, wherein the second peak wavelength is 550 nm.
 13. The endoscopelight source device according to claim 10, wherein the light pathcombiner comprises a dichroic mirror configured to combine the lightemitted along the first light path with the light emitted along thesecond light path.
 14. The endoscope light source device according toclaim 13, wherein a cutoff wavelength of the dichroic mirror is awavelength between the first peak wavelength and the second peakwavelength.
 15. The endoscope light source device according to claim 10,wherein an intensity of the second peak wavelength in the special lightis less than half of an intensity of the first peak wavelength.
 16. Theendoscope light source device according to claim 10, further comprising:a third light source unit configured to emit blue light having a thirdpeak wavelength in a blue wavelength band; and a fourth light sourceunit configured to emit red light having a fourth peak wavelength in ared wavelength band, wherein the light path combiner is configured tocombine the light emitted along the first light path and the lightemitted along the second light path with light emitted along a thirdlight path by the third light source unit and light emitted along afourth light path by the fourth light source unit to produce thecombined light, wherein, when the first light source unit, the secondlight source unit, the third light source unit and the fourth lightsource unit are driven by the light source drive circuitry to emit lightin the first mode, the combined light is normal light that has a widerange of visible light wavelengths and further has the first peakwavelength, the second peak wavelength, the third peak wavelength andthe fourth peak wavelength.
 17. The endoscope light source deviceaccording to claim 10, wherein the first light source unit comprises afirst light-emitting diode, and the second light source unit comprises asecond light-emitting diode.
 18. An endoscope system comprising: theendoscope light source device according to claim 10; and an endoscope.19. An endoscope light source device comprising: a first light sourceunit configured to emit light in a first wavelength band; a second lightsource unit configured to emit light in a second wavelength band havinga peak wavelength that is different from a peak wavelength of the firstwavelength band; a dichroic mirror configured to combine light emittedalong a first light path by the first light source unit with at leastlight emitted along a second light path by the second light source unitto produce combined light; and light source drive circuitry configuredto control the first light source unit to emit light in the firstwavelength band, and to separately control the second light source unitto emit light in the second wavelength band, in accordance with aplurality of modes, wherein the endoscope light source device isconfigured to supply the combined light to an endoscope, and wherein,when the first light source unit and the second light source unit aredriven by the light source drive circuitry to emit light in a first modeof the plurality of modes, the light in the first wavelength band andthe light in the second wavelength band are emitted at a first intensityratio, and the combined light is normal light that has a wide wavelengthrange in a visible light region, and wherein, when the first lightsource unit and the second light source unit are driven by the lightsource drive circuitry to emit light in a second mode of the pluralityof modes, the light in the first wavelength band and the light in thesecond wavelength band are emitted at a second intensity ratio having arelatively lower proportion of the light in the second wavelength bandthan the first intensity ratio, and the combined light is special light,and wherein a light absorption rate of the special light in a specificbiological tissue is higher than a light absorption rate of the normallight in the specific biological tissue.